The Javan rhinoceros (more precisely Sunda rhinoceros)
or lesser one-horned rhinoceros (Rhinoceros sondaicus) is a member
of the family Rhinocerotidae and one of five extant rhinoceroses. It belongs to
the same genus as the Indian rhinoceros, and has similar mosaic ked skin which
resembles armour, but at 3.1–3.2 m (10–10.5 feet) in length and 1.4–1.7 m
(4.6–5.8 ft) in height, it is smaller (in fact, it is closer in size to the
black rhinoceros of the genus Diceros). Its horn is usually less than 25 cm (10
inches), smaller than those of the other rhino species. Once the most widespread
of Asian rhinoceroses, the Javan rhinoceros ranged from the islands of Java and
Sumatra, throughout Southeast Asia, and into India and China. The species is
critically endangered, with only one known population in the wild, and no
individuals in captivity. It is possibly the rarest large mammal on earth, with
a population of as few as 40 in Ujung Kulon National Park at the western tip of
Java in Indonesia. A second population in Cat Tien National Park in Vietnam was
confirmed as extinct in 2011. The decline of the Javan rhinoceros is attributed
to poaching, primarily for their horns, which are highly valued in traditional
Chinese medicine, fetching as much as US$30,000 per kilogramme on the black
market. Loss of habitat, especially as the result of wars, such as the Vietnam
War, in Southeast Asia, has also contributed to the species' decline and
hindered recovery. The remaining range is within one nationally protected area,
but the rhinos are still at risk from poachers, disease and loss of genetic
diversity leading to inbreeding depression. The Javan rhino is smaller than the
Indian rhinoceros, and is close in size to the black rhinoceros. The body length
of the Javan rhino (including its head) can be up to 2 to 4 m (6.6 to 13 ft),
and it can reach a height of 1.4–1.7 m (4.6–5.8 ft). Adults are variously
reported to weigh between 900 and 2,300 kg (2,000 and 5,100 lb), although a
study to collect accurate measurements of the animals has never been conducted
and is not a priority because they are endangered. There is not a substantial
size difference between genders, but females may be slightly bigger. The rhinos
in Vietnam appeared to be significantly smaller than those in Java, based on
studies of photographic evidence and measurements of their footprints. Like the
Indian rhino, the Javan rhinoceros has a single horn (the other extant species
have two horns). Its horn is the smallest of all extant rhinos, usually less
than 20 cm (7.9 inches) with the longest recorded only 27 cm (10.5 in). The
Javan rhinoceros does not appear to often use its horn for fighting, but instead
uses it to scrape mud away in wallows, to pull down plants for eating, and to
open paths through thick vegetation. Similar to the other browsing species of
rhino (the black, Sumatran and Indian), the Javan rhino has long, pointed, upper
lips which help in grabbing food. Its lower incisors are long and sharp; when
the Javan rhino fights, it uses these teeth. Behind the incisors, two rows of
six low-crowned molars are used for chewing coarse plants. Like all rhinos, the
Javan rhino smells and hears well, but has very poor vision. They are estimated
to live for 30 to 45 years. Its hairless, splotchy gray or gray-brown skin falls
in folds to the shoulder, back and rump. The skin has a natural mosaic pattern
which lends the rhino an armoured appearance. The neck folds of the Javan
rhinoceros are smaller than those of the Indian rhinoceros, but still form a
saddle shape over the shoulder. Because of the risks of interfering with such an
endangered species, however, the Javan rhinoceros is primarily studied through
fecal sampling and camera traps. They are rarely encountered, observed or
measured directly

Taxonomy and Naming

The first studies of the Javan rhinoceros by naturalists from outside of its
region took place in 1787, when two animals were shot in Java. The skulls were
sent to the renowned Dutch naturalist Petrus Camper, who died in 1789 before he
was able to publish his discovery that the rhinos of Java were a distinct
species. Another Javan rhinoceros was shot on the island of Sumatra by Alfred
Duvaucel, who sent the specimen to his stepfather Georges Cuvier, the famous
French scientist. Cuvier recognized the animal as a distinct species in 1822,
and in the same year it was identified by Anselme Gaëtan Desmarest as Rhinoceros
sondaicus. It was the last species of rhinoceros to be identified. Desmarest
initially identified the rhino as being from Sumatra, but later amended this to
say his specimen was from Java.

The genus name Rhinoceros, which also includes the Indian rhinoceros, is derived
from the ancient Greek words ῥίς (rhis), which means "nose", and κέρας (ceras),
which means "horn"; sondaicus is derived from sunda, the biogeographically
region that comprises the islands of Sumatra, Java, Borneo, and surrounding
smaller islands. The Javan rhino is also known as the lesser one-horned
rhinoceros (in contrast with the greater one-horned rhinoceros, another name for
the Indian rhino)

There are three distinct subspecies, of which only one is still extant:Rhinoceros sondaicus sondaicus,the type subspecies, known as the
Indonesian Javan rhinoceros, once lived on Java and Sumatra. The population is
now confined to as few as 40 animals in the wild, Ujung Kulon National Park on
the western tip of the island of Java. One researcher has suggested the Javan
rhino on Sumatra belonged to a distinct subspecies, R.s. floweri, but
this is not widely accepted.Rhinoceros sondaicus annamiticus,known as the Vietnamese Javan
rhinoceros or Vietnamese rhinoceros, once lived across Vietnam, Cambodia, Laos
and into Thailand and Malaysia. The sub specific annamiticus is derived
from the Annamite Mountain Range in Southeast Asia, part of this subspecies'
range. In 2006, a single population, estimated at fewer than 12 remaining
rhinos, lived in an area of lowland forest in the Cat Tien National Park in
Vietnam. Genetic analysis suggested this subspecies and the Indonesian Javan
rhinoceros last shared a common ancestor between 300,000 and 2 million years
ago. The last individual of this population was shot by a poacher in 2010.Rhinoceros sondaicus inermis, known as the Indian Javan
rhinoceros, once ranged from Bengal to Burma, but is presumed to have gone
extinct before 1925. The term inermis means "unarmed", as the most distinctive
characteristic of this subspecies is the small horns in males, and evident lack
of horns in females. The original specimen of this species was a hornless
female. The political situation in Burma has prevented assessment of the species
in that country, but its survival is considered unlikely.

Ecology

The Javan rhino can live approximately 30–45 years in the wild. It historically
inhabited lowland rain forest, wet grasslands and large floodplains. The Javan
rhino is mostly solitary, except for courtship and offspring-rearing, though
groups may occasionally congregate near wallows and salt licks. Aside from
humans, adults have no predators in their range. The Javan rhino usually avoids
humans, but will attack when it feels threatened. Scientists and
conservationists rarely study the animals directly due to their extreme rarity
and the danger of interfering with such an endangered species. Researchers rely
on camera traps and fecal samples to gauge health and behavior. Consequently,
the Javan rhino is the least studied of all rhino species. Two adult rhinos with
their calves were filmed in a motion-triggered video released on February 28,
2011 by WWF and Indonesia's National Park Authority, which proved it is still
breeding in the wild. In April 2012, the National Parks Authority released video
showing 35 individual Javan rhinos, including offspring. The Javan rhinoceros is
a solitary animal with the exception of breeding pairs and mothers with calves.
They will sometimes congregate in small groups at salt licks and mud wallows.
Wallowing in mud is a common behavior for all rhinos; the activity allows them
to maintain cool body temperatures and helps prevent disease and parasite
infestation. The Javan rhinoceros does not generally dig its own mud wallows,
preferring to use other animals' wallows or naturally occurring pits, which it
will use its horn to enlarge. Salt licks are also very important because of the
essential nutrients the rhino receives from the salt. Male home ranges are
larger at 12–20 km˛ (5–8 miles˛) compared to the female, which are around 3–14
km˛ (1–5 mi˛). Male territories overlap each other less than those of the
female. It is not known if there are territorial fights. Males mark their
territories with dung piles and by urine spraying. Scrapes made by the feet in
the ground and twisted saplings also seem to be used for communication. Members
of other rhino species have a peculiar habit of defecating in massive rhino dung
piles and then scraping their back feet in the dung. The Sumatran and Javan
rhinoceros, while defecating in piles, do not engage in the scraping. This
adaptation in behavior is thought to be ecological; in the wet forests of Java
and Sumatra, the method may not be useful for spreading odours. The Javan rhino
is much less vocal than the Sumatran; very few Javan rhino vocalizations have
ever been recorded. Adult Javan rhinos have no known predators other than
humans. The species, particularly in Vietnam, is skittish and retreats into
dense forests whenever humans are near. Though a valuable trait from a survival
standpoint, it has made the rhinos difficult to study. Nevertheless, when humans
approach too closely, the Javan rhino becomes aggressive and will attack,
stabbing with the incisors of its lower jaw while thrusting upward with its
head. Its comparatively antisocial behavior may be a recent adaptation to
population stresses; historical evidence suggests they, like other rhinos, were
once more gregarious. The Javan rhinoceros is herbivorous and eats diverse plant
species, especially their shoots, twigs, young foliage and fallen fruit. Most of
the plants favoured by the species grow in sunny areas in forest clearings,
scrubland and other vegetation types with no large trees. The rhino knocks down
saplings to reach its food and grabs it with its prehensile upper lip. It is the
most adaptable feeder of all the rhino species. Currently, it is a pure browser,
but probably once both browsed and grazed in its historical range. The rhino
eats an estimated 50 kg (110 lb) of food daily. Like the Sumatran rhino, it
needs salt in its diet. The salt licks common in its historical range do not
exist in Ujung Kulon, but the rhinos there have been observed drinking seawater,
likely for the same nutritional need. An estimated 40-60 animals live in the
area on the western tip of Java in Ujung Kulon National Park. Another smaller
population occurs in and around the Cat Loc part (Dong Nai province) of the Cat
Tien National Park in of Vietnam, with maybe as few as six individuals remaining
(R. Steinmetz, M. Khan bin Momin Khan pers. comm.). These populations have not
significantly declined over the last few decades, and the current trend is not
known (Sectionov and Waladi pers. comm.), but no breeding has been observed in
the Cat Loc population for many years (M. Khan bin Momin Khan pers. comm.).
There are no animals currently in captivity, and a total of only 22 individuals
have ever been known to exist in captivity (Rookmaaker et al., 1998).
Population Trend: Unknown The Javan Rhinoceros currently occurs in lowland
tropical rainforest areas, especially in the vicinity of water (Schenkel and
Schenkel, 1969). The species formerly occurred in more open mixed forest and
grassland and on high mountains. Because of its rarity, little is known about
its preferred habitat, but it is certainly not naturally restricted to dense
tropical forest water (Schenkel and Schenkel, 1969). Little is known about the
species' biology and the habitats in which the two remaining populations are
found may not be optimal. The home range size of females is probably no more
than 500 ha, while males wonder over larger areas, with likely limited dispersal
distance. The species is generally solitary, except for mating pairs and mothers
with young (Nowak, 1999). Its life history characteristics are not well known,
with longevity estimated at about 30-40 years, gestation length of approximately
16 months (as with other rhino species), and age at sexual maturity estimated at
5-7 years for females and 10 years for males (Nowak, 1999;
Systems: Terrestrial

Major Threat(s):

The cause of population decline is mainly attributable to the
excessive demand for rhino horn and other products for Chinese and allied
medicine systems (Foose and van Strien 1997). The bulk of the remaining
population occurs as a single population within a national park and the
population size in Ujung Kulon National Park is probably limited to the
effective carrying capacity of the area (around 50 animals). One possible threat
to this population is disease. In addition, such a small population faces a
constant threat from poachers, although there is evidence that current poaching
levels are under control (Sectionov and Waladi pers. comm.). The Cat Loc
population may be too small to be viable, and no breeding has been observed for
many years, and it is possible that the animals are too old to breed. The
population is so small that all the animals could be of the same sex.

Conservation Actions:

It is legally protected in all range states. The species
has been on CITES Appendix I since 1975.

A Rhino Protection Unit (RPU) has been established for the protection of this
species on Java (Sectionov and Waladi pers. comm.). It occurs in two protected
areas: Ujung Kulon National Park on Java and the Cat Loc part (Dong Nai
province) of the Cat Tien National Park in Viet Nam.

There is an urgent need to review the feasibility of a
reintroduction/translocation program, since the only known viable population
occurs in a geographically restricted area of Java. There is also a need to
survey parts of its historical range for the very remote possibility that small
remnant populations exist, especially in parts of Lao PDR or Cambodia. The
population in Cat Loc is probably no longer viable, and requires intensive
management measures in order to survive (perhaps including captive breeding and
re-introductions).